1. Field of Invention
This invention relates generally to integrated circuit (IC) manufacturing using exposed silicon substrates on wafer and, more particularly, to the quality, status, and appropriateness of reticle (mask) during the complicated process of IC development.
2. Description of Related Art
In IC manufacturing, the mask (sometimes called the reticle) is used for exposing silicon substrates on a wafer. This mask in combination with complex photographic equipment plays an important role in the semiconductor IC manufacturing process. Wafer quality and yields are impacted by the mask""s status and quality during the complex wafer-build process. Specifically, the mask""s Piece Of Data (POD) which contains its precise image must be kept without defect and in clean condition, so that the quality of the wafer is not compromised.
Ideally, tool operators thoroughly check the status and quality of the mask as well as making sure the mask is the appropriate one for the specific equipment before assigning the mask to the equipment in an attempt to avoid wafer scrap and reduced yields (These are very costly to the manufacturing process and hinder the overall productivity of the entire wafer-build process.). This manual checking of the mask upon each assigning is time consuming, inefficient, and expensive, and the check itself can lead to mask damage.
Currently, there are several different scales of reticle (ex. 2X, 4X, 8X, etc.) in use in FABS. It is important to assign the correct scale and pellicle for the specific machine (match of capabilities) to avoid wafer scrap. Unfortunately, it is very hard to visually differentiate between the different scales as their appearance is very similar. Because of this, a tool operator might mistakenly manually assign the wrong scale mask to the equipment which undetected leads to scrap.
A new automated method and system to more efficiently reduce reticle errors and avoid scrap in a cost-effective way is required. A process to automatically check to make sure pre-defined mask criteria (including usability, appropriateness of scale for assigned equipment, and last clean time of the POD) are met before allowing the mask to be loaded into the equipment is needed.
In U.S. Pat. No. 6,309,944 (Sheng et al.) an overlay matching method that provides alignment of layers of wafers is discussed. In U.S. Pat. No. 6,256,550 (Wu et al.) a manufacturing control method and system for handling semiconductor articles is discussed. In U.S. Pat. No. 5,528,510 (Kraft) a process control system and method using a tuned model control is discussed. In U.S. Pat. No. 4,974,166 (Maney et al.) a system for storing, transporting, and processing semiconductor articles is discussed.
This invention""s overall objective is to provide a software system and method for the automatic control of mask screening for usability and correctness of reticle scale for the specific equipment with the result of improved wafer quality and less scrap. A more specific objective is for a mask to be assigned to the equipment. Another objective is to provide a database in which to store the mask""s parameters. Still another objective is to define the automatic checking criteria for the mask""s parameters for comparison in the database.
Yet another specific objective is to provide a trigger function that automatically begins the checking of the mask. It is a final objective to allow loading of the mask into the equipment only when the set of parameter checks have been satisfactorily met.